Oil Reserves, Oil Resources, Petroleum Reserves, Proven Reserves
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Oil reserves are an assessment of crude oil quantities that can be recovered from underground reservoirs. Such assessments require information about the quantity of oil available and the recovery factor. Some part of the “oil in place” in a reservoir may be non-extractable. In fact, only a small portion of the oil in place can be brought to the surface, given the peculiar characteristics of oil reservoirs and limitations of the petroleum extraction technology.
There are two main classifications of oil reserves – proved and unproved.
- Proved reserves are those that are expected to be recoverable (with at least a 90% probability). Oil reserves are classified as proved on the assumption that the economic and political conditions and technology remain constant. Proved reserves are often referred to as P90 or IP.
- Unproved reserves are those that are not expected to be recoverable, mainly due to technical, contractual or regulatory uncertainties.
Table of Contents
World Oil Reserve Locations
The Middle East is estimated to have more than half of the total oil reserves in the world.
Proved oil reserves (in 1,000 million barrels):
| rank | country | end 2006 | percent of total |
| 1 | Saudi Arabia | 264.3 | 21.88% |
| 2 | Iran | 137.5 | 11.38% |
| 3 | Iraq | 115 | 9.52% |
| 4 | Kuwait | 101.5 | 8.40% |
| 5 | United Arab Emirates | 97.8 | 8.09% |
| 6 | Venezuela | 80 | 6.62% |
| 7 | Russian Federation | 79.5 | 6.58% |
| 8 | Libya | 41.5 | 3.43% |
| 9 | Kazakhstan | 39.8 | 3.29% |
| 10 | Nigeria | 36.2 | 3.00% |
| 11 | USA | 29.9 | 2.47% |
| 12 | Canada | 17.1 | 1.42% |
| 13 | China | 16.3 | 1.35% |
| 14 | Qatar | 15.2 | 1.26% |
| 15 | Mexico | 12.9 | 1.07% |
Source: Statistical Review of World Energy, June 2007
How much of the Oil Reserves are Left?
Claimed reserves among OPEC producers have surged since 1980. Saudi Arabia doubled its reserves from 168 to 255 Gbbl in 1988. Iran raised its proven reserves by around 30% to 130 Gbbl in 2002. Kuwait increased its proven reserves from 67 Gbbl to 92 Gbbl in 1983. The UAE almost tripled its reserves from 33 Gbbl to 97 Gbbl in 1985-1986, whereas Iraq tripled its oil reserves to 100 Gbbl in 1986-1987. According to CIA figures, the world’s top five petroleum reserves are in Saudi Arabia, Canada, Iran, Iraq and Kuwait. The estimated amount of reserves is 266, 178, 138, 115, and 104 trillion barrels, respectively. The average life of each reserve is around 115 years.
Issues in Estimating Oil Reserves
Geology and the quality of the reservoir as well as the present technological level are the major issues in accurately estimating oil reserves. While reserve growth is reported in several fields, this is usually due to statistical reasons (inaccurately estimated oil reserves).
